Insulator



July 16, 1935. E, H. FISCHER 2,008,414

INSULATOR Filed Dec. 4, 1931 NVENTOR Lrzzgene/yf/ificher M ATT NEY Patented July 16, 1935 UNITED STATES PATENT orrrcr:

INSULATOR Eugene H. Fischer, Derry, Pa. Application December 4, 1931, Serial No. 578,889 4 Claims. (Cl. 173-318) My invention relates to insulators and particularly to suspension insulators of the cap-and-pin type.

It is an object of my invention to provide an insulator wherein the various elements are so disposed and shaped that the internal forces are distributed to materially improve the strength and durability of the insulator.

Figure 1, of the accompanying drawing, is a view in side elevation of an insulator embodying my'invention, and

Fig. 2 is an enlarged detail view, partially in elevation and partially in section of a portion of the insulator of Fig. l.

The insulator comprises, in general, a dielectric element 2, a cap terminal element 3 and a pin terminal element 4 all disposed in a usual substantially telescopic or interfitting relation.

The dielectric element 2, preferably of porcelain, comprises a surface creepageflange 6 and a head portion of substantially cup-shape having an end wall 8 and a longitudinal side wall 9 from the open end of which the flange 6 diverges.

The inner and outer surfaces of the side wall 9 are provided with laterally-extending longitudinally-spaced projections I constituting, in effect, annular ridges formed, preferably, by rolling while the porcelain is in the plastic state. Obviously, such projections may be in the form of a single continuous helical ridge or a multiplicity of annularly discontinuous projections, such as might be provided by sand or other particles glazed in position.

The first few of the ridges or projections Hi, from the top down, on the inner surface, and from the bottom up, on the outer surface, of the wall 9, are of gradually increasing lateral extent and the remainder thereof are preferably of substantially the same lateral extent substantially equal to the greatest of the graded projections.

The cap terminal 3, preferably of metal, has a usual socket portion l2 at its upper closed end for attachment to a ball head, similar to the ball head M of the metal pin 4, of the next adjacent insulator or other member with which the insulator cooperates. Other means, such as the usual clevis, may be substituted for the socket portion l2.

The cap 3 further comprises a plurality of annular inner-surface steps l5, extending upwardly from its lower end, that slope relative to the longitudinal axis of the insulator and appear as substantially parallel lines in any vertical plane through the longitudinal axis of the insulator, as shown adjacent to the right-hand side of Fig. 2. An annular surface between the surfaces I is represented by a line I6 that is substantially normal to the lines representing the surfaces I5.

The pin 4 comprises an enlarged head ll having a downwardly and inwardly-sloping surface [8, a shank 20 joining the head H and extending to the ball head l4 thereof. A portion of the shank 20 is preferably slightly tapered so that its diameter is slightly less adjacent to the head I! than at the exposed portion of the shank.

Yieldable elements 22 and 23, of usual character, are disposed, respectively, between the cap and the dielectric head and between the dielectric head and the pin.

Molded bodies 24 and 25, preferably of cement, are, respectively, disposed between the cap and the dielectric head and between the dielectric head and the pin.

In the above-described structure, the surfaces I8 and I5 are substantially parallel, so that opposite longitudinal forces, in this case tension forces, on the cap and pin terminals are normally translated into substantially parallel compression forces between, and normal to, the surfaces l5 and I8 for a substantial distance along the insulator.

The surface I8 is slightly curved to compensate for the different radial thicknesses of the molded body 25. The upper part of the surface It imposes less stress on the thin section of the body 25 by reason of the fact that it more nearly approaches parallelism to the inner surface of the Wall 9, and the remaining portion of the surface IB imposes gradually more stress, as the body 25 increases in thickness. This construction is provided to prevent cracking of the porcelain adjacent to the intersection of the walls 8 and 9.

The surfaces I5 may also be slightly curved but, by reason of the greater diameter and mass of the molded body 24, such curvature does not make sufficient practical difference to warrant the added expense.

The surfaces 15, being radially offset with the surface l6 therebetween normal thereto in the direction of the compression forces, act as a single surface beginning at the lower edge of the cap and extending as far as the upper end of the upper surface [5 but are offset to reduce the bulk of the molded body 24 and to render the latter of more uniform radial thickness. This feature tends toward uniformity of compression in all of the material between the surfaces l5 and I8.

However, the top of the surface [8 is above the top inner ridge l0 and the bottom of the lower surface I5 is below the lower outer ridge II]. If, in view of this feature, the ridges Ill were all of the same lateral extent, or, if there were no ridges at all, there would be sharp lines of demarcation in the dielectric and molded bodies between the zone where these bodies are traversed by the diagonal compression forces and the portions above and below this zone. Thus, bygrading the ridges, as described, there is a moregradual introduction of the diagonal compression forces into this zone from above and from below,

there being still a substantial thickness of the frusto-conical compression zone in which the" forces are substantially equal or uniform. A;

similar effect may be obtained by varying the slope of the side surfaces of the ridges, the distances therebetween, or by a combination of these.-

features.

".It iscontemplated to fill the spaces between the ridges' l E], when metallic glaze is employed on the" dielectric surface and solder is employedas the molded bodies, because this constructionis of exceptional strength along the dielectric surface, but, when cement, or similar material is employed, ridges or sand particles are provided to add shearing strength. 7 There is a substantial quantity of the molded body 25, adjacent to the lower inner portion thereof, that is of little benefit, sofar as adding to the effici ncy of the insulator is concerned, butit is not commercially efficient to remove it or to substitute other material in its'place. "It ordinarily clings to the shank 20 so that, under heavy load, when the pin 4 pulls out of its original position by an infinitesimal amount, cracks are caused in the body 25 below its compression zone and transmitted upwardly into this zone. 7 i 1 By slightly divergingly tapering the shank from the head ll downwardly,'the above-mentioned cracking is avoided by causing the shank to pull away from the cement body.

While Ihave shown and described particular forms of my inventionfchanges may be effected therein. without departing from thespirit and scope thereof, as set forth in the appended claims.

I claim as my invention:

1. A suspensioniinsulator comprising a dielectric member of substantially inverted cup-shape, a capmember surrounding the top a'ndside wall of said dielectric member and having an inwardly sloping peripheralflange, a load receiving pin having an enlarged head portion disposed within" through the side wall of said dielectric member,

and means on the inner and outer faces of said side Wall for grading the distribution of said compressional forces along said side Walls, said means comprising a series of annular .ridgesrounded incross-section and of graded. lateral dimension projecting into the molded material. i

2. A suspension insulator comprising a dielectric member of substantially inverted cup-shape, a metallic cap surrounding the top and side wall of said dielectric member and having an inwardly sloping peripheral flange, a load-receiving pin having an enlarged head portion disposed within said dielectric member, and bodies of molded material disposed between said members for maintaining them in spaced relation, the peripheral flange on'said cap and the enlarged head portion on said pin being so proportioned and related that tensional forces acting on said pin result in forces of compression between said pin and cap through the side wall of said dielectric member, and means on a face of said side wall for grading the distribution of said compressional forces along said side wall axially of the insulator, said means comprising a series of annular ridges rounded in cross-section rolled into the sidewall of said dielectric member and varying in'height from a minimum-adjacent to an edge of the ridged portion.

3. A suspension insulator comprising a dielectric member of substantially inverted cup-shape, a metallic cap surrounding the top and side wall of said dielectric member and having an inwardly sloping peripheral flange, a load-receiving pin having an enlarged head portion disposed within said dielectric member, and bodies of molded material disposed between said members for maintaining them in spaced relation,

the peripheral flange onsaidcap and the enlarged head portion on said pin being so proportioned and related that tensional forces actbetween said pin and cap through the side wall of said dielectric member, and means on a face of said side wall for grading the distribution of said compressional forces along said side wall axially of the insulator, said means comprising a 'seriesfof annular ridges presenting in profile a smooth sinuous contour and varying in height from a minimum 'height at an edge of'the ridged area. a

4. A suspension insulatorcomprising a dielectric member of substantially inverted cup-shape, a metallic cap surrounding the top and side wall of said dielectric member and having aninwardly taining them in spaced relation, the peripheral flange on said cap and the enlarged head portion on said pin being soproportioned and related that tensional forces acting on said pin result in forces of compression between said pin and cap through the side Wall of said dielectric member, andmeans on a face of said side Wall for grading the distribution of said compressional forces along said side wall axially of the insulator, said means comprising a series of annular ridges rolled into the side wall and varying in height from a minimum adjacent to an edge of the ridged portion.

- EUGENE H. FISCHER. 

